In many industrial processes it is necessary to form circular blanks from sheet material, for example; to form circular blanks of paper to be formed into paper cups, or to cut circles of metal, fabric, etc. for other purposes. The objective must obviously be to position the circular cuts on the sheet so that the maximum amount of material is utilized and so that there is minimum waste of sheet material. Some manufacturers cut circles for sheet stock and other cut circles directly from roll stock.
The prior art, as far as we are aware, while occasionally seeking to stamp, or cut, a plurality of circles outlining a rectangle, with the lateral, aligned rows normal to the longitudinal edges of the sheet, and in parallelism, from a continuous web having parallel longitudinal side edges has conventionally and normally sought to cut such a rectangular pattern of rows of circle s from lifts of superposed rectangular sheets by a suitable gang die cutter. The term "gang die cutter" means a die block containing one or more cutting heads, cutting dies, or the like for simultaneous cutting.
The efficiency of such a cutting pattern can be measured by computing the ratio of the amount of raw sheet material utilized in the circles themselves divided by the total raw material of the original sheet. ##EQU1## Waste is defined as 100% minus raw material utilization.
In order to improve material utilization and thereby reduce waste, some manufactures cutting several sizes of circles from rectangular sheets, or webs, have attempted to group several sizes of circles on one rectangular sheet. While this can usually be shown to be an improvement in utilization over a rectangular pattern from which only circles of identical diameter are cut, it involves special collection and handling operations thereby iincreasing cost while reducing waste only slightly.
In U.S. Pat. No. 126,812 to James of May 14, 1872 a method for cutting soles from a side of leather is disclosed. The patentee improves over his prior art by arranging lateral rows of identical soles normal to the longitudinal edges of the pattern; by reversal of toe and heel in alternate longitudinal rows, and by cutting off a portion of each heel to achieve superior economy of material. Mutilation of the circles would not be a successful solution to the problem of maximum production of identical circles from rectangular sheets.
We are aware that angular sheet cutter apparatus is commercially available which can cut square, rectangular or parallelogram shaped sheets. For example, a "Beck Angular Sheet Cutter" made by Charles Beck Machine Corporation of Church Road, King of Prussia, Pa. However, the cutter of such apparatus is normally angularly adjustable only up to 22.degree.which angle would not be satisfactory for the sheets of this invention.